In general, a screw conveyor conveys and supplies an object to be conveyed that has been introduced in a casing, by rotation of a screw. However, if highly adherent particulate matter is conveyed as the object to be conveyed by the screw conveyor, the particulate matter may be deposited on and become adhered to the bottom portion of the casing, resulting in production of a rigidly settled object. Due to this, an edge of a screw blade may be subjected to wear when contacting the settled object, and conveyance efficiency may be decreased due to an increase in torque. In some cases, a supporting base such as a bearing block for supporting the screw may be damaged, and the conveyance may be impossible.
To solve this problem, in a known example of a screw conveyor, a screw conveyor chips off the deposited and adhered particulate matter by lifting the screw shaft during rotation to prevent a rigidly settled object from being produced.
Also in a screw discharger used for discharging reduced iron from a movable hearth type reduction furnace, there has been provided a method of lifting up a screw in accordance with the thickness of a settled object produced on a movable hearth. Accordingly, the screw may be prevented from being subjected to wear, and a discharge efficiency many be maintained, thereby stabilizing the operation.